Processing of finely divided particulate materials

ABSTRACT

A mass of finely divided material is confined in a chamber. Two rollers are arranged for rotation in the chamber in axial parallelism with one another and define with each other a narrow longitudinally extending gap. At least one of the rollers has a circumferential wall composed of gas-permeable porous material. This one roller is hollow and arranged to communicate with a source of underpressure so that, as the roller rotates, the particulate material is attracted onto its outer surface forming a layer thereon which is subjected to substantial compaction when it passes through the gap between the two rollers. The rollers rotate in opposite direction. The compacted material is removed from the outer surface of the roller or rollers and subdivided into portions of desired size.

United States Patent [1 1 Reinhardt et al.

[4 1 Oct. 2, 1973 PROCESSING OF FINELY DIVIDED PARTIC ULATE MATERIALS [75] Inventors: Helmut Reinhardt, Weiss near Cologne; Berndt Brandt; Albert Peters, both-of Wesseling-Berzdorf, all of Germany [73] Assignee: Deutsche Gold-Und Silber- Scheideanstatt vormals Roessler, Frankfurt am Main, Germany [22] Filed: July 12, 1971 [21] Appl. No.: 161,790

Related U.S. Application Data [62] Division of Ser. No. 874,654, Nov. 6, 1969.

[30} Foreign Application Priority Data Nov. 8, 1968 Germany P 18 07 714.0

[52] U.S. Cl 425/223, 425/85, 425/308, 425/316, 425/812 [51] Int. Cl. B29c 15/00 [58] Field of Search 425/DIG. 62, 75, 425/223, 308, 315, 316, 85; 262/297, 323,

[56] References Cited UNITED STATES PATENTS 2,689,653 9/1954 Ohlstrom 162/297 X Primary Examiner-H. A. Kilby, Jr. Attorney-Michael S. Striker [57] ABSTRACT A mass of finely divided material is confined in a chamber. Two rollers are arranged for rotation in the chamber in axial parallelism with one another and define with each other a narrow longitudinally extending gap. At least one of the rollers has a circumferential wall composed of gas-permeable porous material. This one roller is hollow and arranged to communicate with a source of underpressure so that, as the roller rotates, the particulate material is attracted onto its outer surface forming a layer thereon which is subjected to substantial compaction when it passes through the gap between the two rollers. The rollers rotate in opposite direction. The compacted material is removed from the outer surface of the roller or rollers and subdivided into portions of desired size.

12 Claims, 2 Drawing Figures PATEN EB 3.762.851 SHEET 1 UF 2 mun Aid

M mm WMMP T KN N On R 57v mo uw w PATENTED 2W5 3.762.851

' SHEET 2 OF 2 INVENTOR I uT kE/MM l 7" ATTORNEY PROCESSING OF FINELY DIVIDED PARTICULATE MATERIALS CROSS-REFERENCE TO RELATED APPLICATION This application is a division of our application Ser. No. 874,654, filed Nov. 6, 1969 and entitled Processing of Finely Divided Particulate Materials.

BACKGROUND OF THE INVENTION The present invention relates generally to the processing of finely divided particulate materials, and more specifically to the processing of such materials which requires pre-condensing and subsequent compacting of such materials into desired shapes. The im vention relates to an apparatus for effecting such processing.

In many instances the processing of finely divided particulate material, such as pulverulent or finecrystalline and organic materials, frequently depends upon the possibility of increasing the volumetric weight of such materials without destroying or adversely influencing their specific characteristics which depend upon the fine division of such materials. This is particularly true of highly dispersed surface-active filler materials, such as silicium oxide, carbon black, aluminum oxide, aluminum silicates and calcium silicates, all materials which are used in very large quantities in various industries.

The problems involved in the processing of these materials are not insignificant. On the one hand, in their finely divided state they require relatively large amounts of space for storage and transportation, an obvious disadvantage. Furthermore, they tend to dust and to undergo uncontrollable caking, bothv of which are of course characteristics of their finely divided state which are clearly detrimental to economic handling and proper processing.

Industry has attempted to find solutions to these problems, and particularly to impart to such finely divided materials a state in which their specific characteristics-suCh as the ability to disperse in the case of finely divided active filler materialsare fully retained while the space required for storage and transportation is substantially reduced, and dusting during filling, metering and processing is largely eliminated. It has been proposed to achieve this by transforming the finely divided materials into agglomerates of certain configuration and dimension by subjecting them to mechanical pressure. This has been found to be practical in a continuous operation only if the significant quantities of gases present in highly dispersed materials are first removed, because otherwise it is not possible to obtain agglomerates with sufficient adhesion under mechanical pressure. It has been found, for instance, that it is impossible to obtain the desired compaction and adhesion simply by passing such materials between two metal rollers which subject them to mechanical compression. Therefore, gas removal and pre-condensing has been resorted to, utilizing in known continuously operating apparatus of the type in question pressuretype conveyor screws, rollers or pairs of rollers provided with radial projections or provided on the surface of at least one roller with profiling. However, it has been found that the degassing or outgassing effect and compaction obtainable with such apparatus, which for the actual compaction utilizes a pair of pressure rollers. is inadequate compared to the complexity and expense of the apparatus involved.

A further approach which has been tried is to deposit the material to be compacted onto hollow rollers, socalled filter rollers. whose circumferential wall is gaspermeable and whose interior is subjected to underpressure. The gas is thereby withdrawn from the deposited material and the material is supplied by the filter rollers to the compacting gap between a pair of pressure rollers. Various modifications have been proposed for this basic approach but in each case the gap between the pressure rollers--in which the material is subjected to compaction-is fixed. This approach is limited in itsapplicability because it permits only the production of compressd blanks, as, the compacted bodies made from the compacted finely divided particulate materials will hereafter be called for the sake of convenience, without specific form and only within a rather broad range pf grain sizes. A further disadvantage is that the compacted blanks obtained in this manner have a widely varying breaking resistance, a fact which is of particular disadvantage if the compacted blanks are of filler material which is intended for certain applications, for instance for use in rubber mixtures, because with the mixing procedure used in the produciion of rubber mixtures the compacted blanks can be broken down only partially to the original grain size. The result of this is an inadequate dispersal of the filler material and the resulting typical formation of pockets and cavities in the vulcanized goods.

In addition certain materials, for instance light reinforcing filler materials such as SiO2, can be compacted only to a bulk density of approximately 250 g/ 1 in the apparatus known from the prior art and utilizing the socalled filter rollers, because the low mechanical strength of the fabrics used for the circumferential walls of the filter roller makes it impossible to utilize higher compacting pressures. This is quite aside from the fact that even at these lowered operating pressures the fabrics must be very frequently replaced.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to overcome the aforementioned disadvantages.

A more particular object of the invention is to provide an apparatus for processing finely divided particulate materials which is not subject to the disadvantages outlined before.

A concomitant object of the invention is to provide such an apparatus which enables continuous operationand the production of compacted blanks of specific desired shape and size with a defined narrow range of breaking resistance and increased bulk weight.

in pursuance of the above objects, and others which will become apparent hereafter, one feature of the invention resides in the novel apparatus in which. briefly stated, a mass of finely divided material is confined adjacent to the gas-permeable circumferential wall of a rotatable roller having a hollow interior. The roller is thereupon rotated and subjected in its interior to underpressure so as to attract the material by suction to The roller having the gas-permeable circumferential wall, hereafter for the sake of convenience called the filter roller, may rotate partially or completely in the material to be compacted, and the same is true of the other roller. The thickness of the layer may be maintained constant by removing excess attracted material from the layer before increments of the layer enter into the gap between the two rollers. In accordance with the invention, one of the two rollers is biassed towards the other with a biasing force which is preferably maintained at constant level. The other roller may also be 7 a filter roller or it may be a roller having a known gaspermeable circumferential wall. In any case, the layer is compacted passage of the gap between the two rollers so as to be reduced by at least one half of its original volume and is deformed-by profiling provided on the circumferential wall of at least one of the rollers-into compacted blanks of desired shape and configurttion and defined range of breaking strenght.

It is desired and advantageous accordingto the present invention thatthe dwell time of the material of the layer, that is of the material of which each successive increment of the layer is composed which enters the gap between the two rollers, be below approximately 5 second,, a time value which of course depends upon the roller circumference and the speed of rotation of the rollers.

In accordance with the invention it is not necessary that two rollers be provided having a gas-permeable or porous circumferential wall, or that even the two rollers of the same type be rotated oppositely one another. However,for granulating purposes it is desirable and preferable that one of the two rollers has a profiled surface of circumferential wall. Depending upon the profiling, compacted blanks of certain configuration are obtained, for instance granules, little rods, tablets and the like. For instance, if the profile is half-moon shaped, then the compacted blanks will be similarly configurated. These compacted blanks may then be reduced to the desired dimensions in a cutting device of known construction, for instance in aso-called rotary disc breaker. Because of the profiling on at least one of the rollers, at least two dimensions of the resulting product are already established before the g tting device acts upon the compacted blanks.

The novel features which are considered as characteristic of the invention are set forth in partular in the pp cltLms. The.immune.itsslflb wcverboth as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partially sectioned diagrammatic perspective view of an apparatus according to the present invention; and

FIG. 2 is a partly sectioned somewhat diagrammatic perspective view illustrating one embodiment of a roller for use in the apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, the apparatus comprises a housing 1 having two transversely spaced walls In. Mounted in the housing 1 is a filter roller 2, for instance of the type which will bediscussed more specifically with reference to FIG. 2. The roller 2 is hollow, and arranged for rotation in axial parallelism with the roller 2 is the roller 3 rotating in the direction opposite to the roller 2, as indicated by the arrows respectively associated with the two rollers. The circumferential wall of the roller 3 is not gas-permeable, and the roller 3 is therefore not designated as a filter roller as is the case with the roller 2. Instead, the circumferential wall of the roller 3 is provided on its exterior with a half-moon shaped longitudinal profile 4, shown in cross-section.

According to the invention the dimensions of the housing 1 are so selected that the spacing between the filter roller 2 and the housing wall 1 in direction normal to the longitudinal axis of the filter roller 2 is substantially greater than the gap between the rollers 2 and 3.

The shaft 15 about which the filter roller 2 rotates is hollow and a suitable source of underpressure, i.e. suction may be connected with it in order to obtain underpressure in the interior of the filter roller 2.

Pressure-measuring transducer 13a and a P1 regulator which iscoupled with an indicator device 130, permit regulation of the value of underpressure applied to the interior of the filter roller 2, via a valve 3e.

Slide bearings 9 journal the shaft 15 of the fitter roller 2, permitting movement of the latter in the direction towards eta ay m FQUS 3- assins evices 7, which here are illustrated as being of hydraulic type but which could be mechanically or pneumatically operated, act upon the bearings 9 and bear upon a supp s r u whisbislqsatssi sxtqii rly ttawa!!! 1a of the housing. A hydraulic pump 12a provides the necessary biassing force whose value is registered on the indicators 12b. If a pressure increase takes place in the system as a result of changes in the size of the gap between herqllsts 2....anslk9a9sstlb increased ness of the layer of material as it enters the gap or by other factors, the increased pressure can yield and fluid escapes into the two reservoir bulbs which are provided. Two pressure relief valves 12d are provided intermediate the reservoirs 12c and the biassing devices 7 in order to assure that the applied isodynamic pressure" is so reduced only after it reaches a certain level. If the manually operated hydraulic pump 12a is replaced with an electrically operated pump, then a maximum-minimum or limit switch 12: must be provided for effecting automatic regulation of the desired biassing pressure.

A hopper l4 communicates with the interior space 5 in the housing 1 for introducing into the space 5 the finely divided particulate material whichis tobe compacted. When underpressure is applied to the interior of the rotating filter roller 2, the particulate material is attracted to the outer surface of the circumferential wall of the filter roller 2 to form a layer thereon which then passes into and through the gap between the rollers 2 and 3. It is desirable to provide an adjustable and shiftable doctor blade 10 above the filter roller 2 for removing material from the attracted layer in excess of a predetermined thickness, in order to pro- FIG. 2 illustrates a specific embodiment of a filterroller for use in the apparatus according to the present invention. Reference numeral identifies the hollow shaft a portion of which is provided with bores 15a. There are provided two side walls or end walls 17 of disc-shaped which are gas-tight with the hollow shaft 15 at the opposite axial sides of the region in which the bores 15a are provided. There is further provided a circumferential wall 16 of cylindrical configuration which is provided with a plurality of small bores or other apertures 16a. The wall 16 is fluid-tightly connected with the end walls 17, for instance by welding, and in the same manner the walls 17 may be connected with the shaft 15.

Provided on the exterior of the cylindrical circumferential wall 16, which may also be called the inner circumferential wall 16, is an outer circumferential wall composed of a plurality of plates 18 of sintered material, for instances metallic sintered material, synthetic plastic sintered material or ceramic sintered material. These plates 18 abut one another and, insofar as they are composed of weldable material, are welded to the inner circumferential wall 16 as to one another where they abut. However, screw means may also be provided for securing the blades 18 to the inner circumferential wall 16. The inner circumferential wall 16 is provided with interiorradial reinforcing ribs 19 for increasing the strength and stability of the roller, but helically convoluted ribs or axially extending ribs may also be provided, or any combination of the three. Reference numeral 20 identifies the inlet opening of the hollow shaft 15 at which underpressure may be applied.

It has been found that the production of compacted blanks with defined range of break resistance is facilitated by maintaining a constant level of biassing pressure of the rollers 2 and 3 towards one another. In order to obtain only small fluctuations of this range it is advisable to mount one or both of the rollers in the manner shown in FIG. 1, that is in such a manner that the gap width can change automatically in dependence upon the thickness of the layer carried by the filter roller, or the compaction of the material in the gap, or other factors, thereby assuring that the coacting and compression is always effected with identical mechanical pressure. Furthermroe, such a construction of course reduces the possibility of breakdown of the apparatus.

The level of this isodynamic pressure depends in each individual case upon the particulate material to be compacted, its moisture content and the degree of compacting which is desired. In the case of white filter materials, such as silicium dioxide, the moisture content is for instance desirably not below 1 percent.

The optimum break resistance of the compacted blanks made from a given particulate material depends upon the intended use and can readily be determined by empirical means. For instance, it has been found that Si0 granulates produced in accordance with the present invention have adequate transport stabiltiy and maximum dispersion characteristics in a test rubber mixture if a break resistance to pressure between 100 and 500 pond (p) is obtained in the compacted blanks, measured with the hardness tester according to German Auslegeschrift l 374 254. The term breaking pressure is intended to mean the pressure in ponds which is necessary to abruptly destroy a granulate of 2 3 mm grain size.

The dispersion characteristics of SiOg compacted blanks made in accordance with the present invention may for instance be determined in a test mixture colored with ferrous oxide red. In this case, the test mixture is introduced into a mixer of the internal type and under identical circumstances one bath of test mixture has admixed therewith silicium dioxide granulate made according to the present invention whereas another batch has admixed therewith for comparison purposes a simple optical comparison indicates if and to what extent dispersion has been improved. It has been found, surprisingly, that if the breaking pressure of the compacted silicium dioxide blanks is set to between 200 and 250 ponds, the dispersion in the test mixture is substantially better than in the test mixture to which the silicium dioxide poder was added.

For instance, if the original finely divided particulate mateaal is a Si0 powder with primary particle size smaller than 50 p. and with a bulk weight of approximately g/l, then a SiO granulate according to the present invention and having breaking pressure values between 200 and 250 ponds may be produced under approximately the following circumstances:

roller pressure approximately 0.1 -0.5 t/cm roller gap If the roller diameter is for instance 200 mm and the length of the rollers is 300 mm, the production amounts approximately 0.3-0.95 kg/cm2 approximately 6 m6/cm x h to approximately 250 kg/h granulate having a bulk weight of approximately 330 g/l. During the transportation of the particulate material on the surface of the filter roller into the roller gap, that is prior to the compacting which takes place in the roller gap itself, a precomacting or precompressing to a bulk weight of approximately 250 g/l is obtained in this case.

If for instance one of the rollers has a half-moonshaped longitudinal profile in its outer circumferential surface with dimensions of 6 X 2 mm, then a finished granulate with approximately the following screen analysis is obtained by breaking the rod-shaped SiOz compacted blanks falling out of the gap between he rollers in a conventional rotary disc breaker and subjecting them subsequently to screen removal of the fines smaller than 0.5 mm;

Particale Size Enlarged photographs of the individual sieve or screen fractions of the finished granular show that the form obtained for the compacted blanks during compaction in the gap between the rollers is readily visible in case of the fraction 3 5 mm, and that it is still readily identifiable in case of the 2-3 mm fraction. This means that the identifiably shaped granulate quantity amounts to 65 percent, that is the total of the fractions 3-5mmand2-3mm.

It will be appreciated that unlike the embodiment illustrated in FIG. 1, it is possible to mount the filter roller 2 for rotation but not for shifting movement, and

to mount the roller 3 for such shifting movement. However, the embodiment illustrated in FIG. 1 is preferred.

It is advantageous in accordance with the present invention that the pores of the material of which the flier eneamrieiitarwan of "manner rollris can posed be so dimensioned that at a predetermined operational load of the suction device an underpressure of constant value in the interior of the filter roller, irrespective of whether the filter roller is partly or completely immerse in the material to be compacted.

I Ti, as illustrated'in the embodiirientof FIGL iIa'r tT tary disc breaker is arranged below the gap between the rollers 2 and 3, then it is advantageous that the cutting 4185 t fll fft v is iiilifi" planes transversely to the elongationof the gap. This is particularly advantageous if the apparatus according to the present invention produces compacted blanks in profiling which extends longitudinally of the rollers.

The material for the porous outer circumferential wall of the filter roller is a suitable sinter material, such as sinter metal, sintered synthetic plastic or sintered ceramic. It is of course not necessary that the ouper circumferential wall consist of the plate-shaped'portions illustrated in FIG. 2, but this enhances the stability.

' it is advantageous, but not absolutely necessary that the spacing of the filter roller from the bottom wall of the housing 1 be at least equal half the roller diameter, and that the lateral spacing between the sinter roller and the housing wall be equal to at least one roller diameter. The doctor blade m er tion ed before may be. adjustably mounted so as to be movable towards and away from the circumferential wall of the filter roller, and it may also be so mounted that its angle with respect to the circumferential wall can be adjusted.

. The pores of theporous material of the outer circumferential wall of the filter roller may have-a diameter of approximately -200 s, preferably between 0-35 s. The thickness of the outer circumferential wall should be at least approximately I 1 mm. At underpressures of .01l.0 kg/cm gas permeability of the outer circumferential wall of the filter roller may be in the region between approximately 0.1 and 7 m 3/cm X h.

The roller for utilization in the apparatus according to the present invention, has certain very definite advantages over the roller used in known apparatus,

namely a long life irrespective of whether it is rotated at low or high rotational speeds, resistance to much higher pressure than are possible with the known constructions, and retention of its shape, that is resistance to being deforined so it is ou t of-round in cross section.

The following examples will further aid in an under-' standing of the invention.

' EXAMPLE 1 approximately 6% Specific weight L9 2.0 Bulk weight 80 110 g/l Vibratory weight I60 200 g/l BET-surface 240 m Primary particle 16 p. diameter The apparatus utilized an isodynamically biassed filter roller and a nonadjusted rotatable non-gas perme- ;of pt. The profile of the counter roller had the dimensions 6X 2. Arranged below the gap between these rollers was a rotary disc type breaker with a spacing between the disc of 3 mm.

Prior to operation of the device the housing was filled v ia the l icmp e r t o approxirnately two-thirds with the pulverulent material to be compacted, a roller pressure of 0.35 t/cm was set and an underpressure of 0.6 kg/cm was applied to the filter roller. The doctor blade arranged above the filter roller was set at a distance of 15 mm from the circumferential wall of the filter roller. Thereupon, both rollers and the disc type breaker were simultaneously started. The rotation of the rollers was so regulated that the medium dwell time of the material to be compacted in the gap between the rollers was approximately 0.15 sec. The width of the gap was approxmy 1 innifThe movements of the filter miter-Hairection normal to the axes of the two rollers, which occurred during the compacting operation, were in the range of between 1 3 mm.

The bulk weight of the p'recompacted particulate material forming a layer on the filter roller prior to enter- 7 ing into the gap was 255 g/l. The output obtained was approximately 260 kg/h granulate having a bulk weight of 330 g/l. The breaking pressuroof the compacted blanks was between 200 and 250 pond.

After screening and classification to particle sizes between 0.5 5 mm, only afine smaller than 0.5 mm amounting to 15 percent was left.

Sieve analysis on a laboratory sieve or screen of commercially available typeshowed the following values in the final product:

Particle Size The granulate portion having an identifiable shape ,(fractio ns, 5, 3-5 mm and 2-3 mm) correspond to 62.6 percent of the total.

. The dispersion ability of the granulate was tested in a red colored test rubber mixture free of vulcanizing additivesi K arab'iider-Plastog'raph was used as dispersion apparatus.

""nefifiatsres thus obtained were subsequently passed, at C and at a gap setting of 1 mm, three times through a laboratory two-roller frame and then rolled out to a thickness of 5-3 mm. The quantity of dispersion was thereupon determined under a light microscope, based upon top-lighted photographsof microtome cuts tken of the rolled-out skin. No pockets or similar irregularities were found. Surprisingly, the degree of dispersion obtained with the Si0 granulates produced according to the present invention was even distinctly better than that obtained in test mixtures which were made with pulverulent starting material.

TEST MIXTURE AND DISPERSION CONDITIONS Quantities \esscl Utili- Mixing volume zation, Temp, time, Components G M1. ml. percent Rpm. C min.

Butyl rubber 1 28 28 50 9O 50 100 10 Iron oxide batch 3 5 5 K1) 140 3 1. 7 1. 7 Granulate 20 10 Total 54. 7 44. 7

Polysarbutyl 301 (Polysar C0., Belgium),Ftype nonstaining, isopren content of 1.6

mol-percent Mooney viscosity, ML 8:85 (at 212 I Consisting of 100 parts polysarbutyl 301 and 50 parts iron oxide rod.

Corporation, New York.

EXAMPLE 2 (COMPARISON TEST) The starting SiO material used in the Example 1 for producing granulates was pressed with a known apparatus of comparable dimensions. Precompression took place via a vertically operated screw and compacting took place in the gap between two oppositely rotating metal rollers whose circumferential walls were provided with wave-shaped serrations. In order to be able to at all obtain a granulate break resistance on the order of 200 pond it was necessary to pass the SiO repeatedly through the gap between the rollers. The production output was only 50 kg/h. The granulate dispersion in the test mixture produced in accordance with Example 1 was significantly poorer than that of the test mixture utilizing the pulverulent starting material. it was a particar disadvantage that the fines O.5 mm obtained on classification in the range between 0.5 5 mm was 50 percent after the first compacting, and could be reduced to approximately percent only by repeated compacting.

it will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of apparatus differing from the types described above.

While the invention has been illustrated and described as embodied in an appratus for processing finely divided particulate matter, it is not intended to be limitedto the details shown, since various modificatons and structural changes may be made without departing in any way from the spirit ofthe present inventlon.

Without further analysis. the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. Apparatus for processing finely divided substantially dry particulate materials comprising wall means defining a chamber adapted to accommodate a mass of asing at least one of said roller means towards the other transversely of said gap for compacting of said layer in response to movement of sequential increments thereof through said gap; and breaker means located below said roller means for recieving said. layer and, breaking up compacted increments of said layer intofragrnents having fixed predetermined length and width dime n- I srons.

2. Apparatus for processing finely'divided substantially dry particulate materials, comprising wall means. defining a chamber adapted to accommodatea massof finely divided particulate material; hollow, first roller means having a gas-permeable circumferential walltand being mounted for rotation relative toand atleast partly immersed in said mass; second roller emans rotatably mounted adjacent said first roller emans and defining therewith an axial gap; biasing means biasing at least one of said roller means towards the other trans-. versely of said gap; suction means communicating with the interior of saidfirst roller means for effecting deposition of a layer on said material on theexterior of said circumferential wall for subsequent compacting in response to movement of sequential.incre-. ments of the layer through said gap; and a disk breaker device for breaking up compacted increments of said layer into fragments of predetermined size, including a plurality of disks mounted below said roller means for rotation in planes transverse to the elongation of said gap.

means; and wherein the smallest distance between said circumferential wall of at least said first roller means and the associated wall of said pair of walls is at least three times greater than the width of said gap.

5. Apparatus as defined in claim I, wherein each of said roller means has an outer peripheral surface, and wherein said outer peripheral surface of said second roller means is provided with closely adjacent axially extending grooves.

6. Apparatus as defined in claim 1 each of said roller means having an outer circumferential surface; and, wherein at least one of said outer circumferentialsurfaces is profiled.

7. Apparatus is defined in claim 1, said chamber having a bottom wall-surface below said roller means, and said first roller means having a given diameter; and wherein the distance between said first roller means and said bottom wall-surface is at least equal to one-half of said given diameter.

' Ap paratus as defined in claim 1 said circumfer ential wall being provided with a plurality of pores having a combined cross-sectional area so selected that said suction means maintains an at least sub stantially constant level of suction in said first roller irrespective of the extent to which the latter is immersed in said mass.

9. Apparatus as defined in claim 1, said first roller means comprising at least one roller including a hollow shaft having an elongated apertured portion, a pair of endwalls fluid-tightly mounted on said shaft at opposite axial ends of said apertured portion, an apertured inner circumferential wall extending from one to the other of said end walls concentric with said portion of said shaft and fluid-tightly connected with said end walls, and said gas-permeable outer circumferential wall mounted on and exteriorly surrounding said inner predominantly outer circumferential wall has a gas-permeability of between substantially 0.l and 7 m lcm when subjected at one side to an underpressure of between substantially 0.01 1,0 kglcm 

1. Apparatus for processing finely divided substantially dry particulate materialS comprising wall means defining a chamber adapted to accommodate a mass of finely divided particulate material; hollow first roller means having porous gas-permeable circumferential wall and being mounted for rotation relative to and at least partly immersed in said mass; second roller means rotatably mounted adjacent said first roller means and defining therewith an axial gap; suction means communicating with the interior of said first roller means for effecting deposition of a layer of said material on the exterior of said circumferential wall; biasing means biasing at least one of said roller means towards the other transversely of said gap for compacting of said layer in response to movement of sequential increments thereof through said gap; and breaker means for located below said roller means for receiving said layer and breaking up compacted increments of said layer into fragments having fixed predetermined length and width dimensions.
 2. Apparatus for processing finely divided substantially dry particulate materials, comprising wall means defining a chamber adapted to accommodate a mass of finely divided particulate material; hollow first roller means having a gas-permeable circumferential wall and being mounted for rotation relative to and at least partly immersed in said mass; second roller means rotatably mounted adjacent said first roller means and defining therewith an axial gap; biasing means biasing at least one of said roller means towards the other transversely of said gap; suction means communicating with the interior of said first roller means for effecting deposition of a layer on said material on the exterior of said circumferential wall for subsequent compacting in response to movement of sequential increments of the layer through said gap; and a disk breaker device for breaking up compacted increments of said layer into fragments of predetermined size, including a plurality of disks mounted below said roller means for rotation in planes transverse to the elongation of said gap.
 3. Apparatus as defined in claim 1, wherein said circumferential wall of said first roller means is composed at least in part of sintered metallic powder.
 4. Apparatus as defined in claim 1, said wall means defining a housing having a pair of spaced walls located at opposite sides of and each extending in at least substantial axial parallelism with said roller means; and wherein the smallest distance between said circumferential wall of at least said first roller means and the associated wall of said pair of walls is at least three times greater than the width of said gap.
 5. Apparatus as defined in claim 1, wherein each of said roller means has an outer peripheral surface, and wherein said outer peripheral surface of said second roller means is provided with closely adjacent axially extending grooves.
 6. Apparatus as defined in claim 1, each of said roller means having an outer circumferential surface; and wherein at least one of said outer circumferential surfaces is profiled.
 7. Apparatus is defined in claim 1, said chamber having a bottom wall-surface below said roller means, and said first roller means having a given diameter; and wherein the distance between said first roller means and said bottom wall-surface is at least equal to one-half of said given diameter.
 8. Apparatus as defined in claim 1, said circumferential wall being provided with a plurality of pores having a combined cross-sectional area so selected that said suction means maintains an at least substantially constant level of suction in said first roller irrespective of the extent to which the latter is immersed in said mass.
 9. Apparatus as defined in claim 1, said first roller means comprising at least one roller including a hollow shaft having an elongated apertured portion, a pair of endwalls fluid-tightly mounted on said shaft at opposite axial ends of said apertured portion, an apertured inner circumferential wall extending from one to the other of said end walls concentric with said portion of said shaft and fluid-tightly connected with said end walls, and said gas-permeable outer circumferential wall mounted on and exteriorly surrounding said inner circumferential wall and at least predominantly composed of sintered material.
 10. Apparatus as defined in claim 9, said sintered material of said outer circumferential wall comprising pores having diameters in the range between substantially 0 - 200 Mu .
 11. Apparatus as defined in claim 1, wherein said outer circumferential wall has a thickness of at least 1 mm.
 12. Apparatus as defined in claim 1, wherein said outer circumferential wall has a gas-permeability of between substantially 0.1 and 7 m3/cm2 when subjected at one side to an underpressure of between substantially 0.01 - 1.0 kg/cm2. 